Limited Feedback Channel Estimation for Multi-User Massive MIMO Visible Light Communications

Abstract

Building on the existing illumination infrastructure, visible light communication (VLC) utilizes light emitting diode (LED) luminaries as wireless access points. The presence of large number of ceiling lights in conference halls, classrooms and similar public places makes possible the implementation of massive multiple-input multiple-output (MIMO) VLC systems in a distributed manner. In order to obtain the full benefits of massive MIMO communications, channel state information must be available at transmitter side. Estimation of downlink channel through pilot signals, if not judiciously designed, requires huge pilot overhead and makes the implementation of massive MIMO system infeasible. In our study, we address the design of massive MIMO VLC systems with a limited number of pilot signals. We explore different pilot arrangements in spatial, frequency, and time domains where interpolation is performed to obtain global channel matrix taking advantage of the indoor environment geometry and layout of luminaries. We consider direct current biased orthogonal frequency division multiplexing as the basis of physical layer and present simulation results to demonstrate the achievable spectral efficiencies for pilot signal arrangements under consideration.